PCRE 7.8 and 8.32 through 8.37, and PCRE2 10.10 mishandle group empty matches, which might allow remote attackers to cause a denial of service (stack-based buffer overflow) via a crafted regular expression, as demonstrated by /^(?:(?(1)\\.|([^\\\\W])?)+)+$/.

Heap-based buffer overflow in PCRE 8.34 through 8.37 and PCRE2 10.10 allows remote attackers to execute arbitrary code via a crafted regular expression, as demonstrated by /^(?P=B)((?P=B)(?J:(?P<B>c)(?P<B>a(?P=B)))>WGXCREDITS)/, a different vulnerability than CVE-2015-8384.

PCRE before 8.36 mishandles the /((?(R)a|(?1)))+/ pattern and related patterns with certain recursion, which allows remote attackers to cause a denial of service (segmentation fault) or possibly have unspecified other impact via a crafted regular expression, as demonstrated by a JavaScript RegExp object encountered by Konqueror.

The compilebranch function in pcrecompile.c in PCRE 8.x before 8.39 and pcre2compile.c in PCRE2 before 10.22 mishandles patterns containing an (ACCEPT) substring in conjunction with nested parentheses, which allows remote attackers to execute arbitrary code or cause a denial of service (stack-based buffer overflow) via a crafted regular expression, as demonstrated by a JavaScript RegExp object encountered by Konqueror, aka ZDI-CAN-3542.